Development and validation of a high throughput and robust LC-MS/MS with electrospray ionization method for simultaneous quantitation of diltiazem and its two metabolites in human plasma: Application to a bioequivalence study.

A high throughput and specific method using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of diltiazem and its two metabolite (N-desmethyldiltiazem and O-desacetyldiltiazem) in human plasma. A one-step liquid-liquid extraction (LLE) with methyl-t-butyl ether (MTBE) involved for the extraction of diltiazem (DLTZ), metabolites (DMeD and DAcD) and internal standard. Analytes were chromatographed on a ACQUITY UPLC BEH C(18) column (100 mm x 2.1 mm, i.d., 1.7 microm) with isocratic elution at a flow rate of 0.2 mL/min using 10 mM ammonium acetate buffer-acetonitrile (25:75, v/v). The Quattro Premier XE LC-MS/MS was operated under the multiple reaction-monitoring mode (MRM) using the electrospray ionization technique. Using 300 microL plasma, the method was validated over the concentration range 0.48-639.9 ng/mL for DLTZ and 0.24-320.1 for DMeD and 0.24-320.7 ng/mL for DAcD, with a lower limit of quantification of 0.48 ng/mL for DLTZ and 0.24 ng/mL for metabolites. The intra- and inter-day precision and accuracy were within 10.0%. The recovery was 77.4%, 76.0%, 74.5% and 74.1% for DLTZ, DMeD, DAcD and Ziprasidone, respectively. Total run time was 2.0 min only.